1What's a Fourth of July celebration without fireworks?
2Brilliant colors exploding in the air.
3The oohs and ahs they elicit on the ground.
4Fireworks are so high-tech these days.
5It's easy to forget they're not a modern invention.
6Historians believe gunpowder, the explosive ingredient in fireworks,
7was invented in China around 1000 A.D.
8It's said that in a famous battle, the Chinese emperor illuminated the sky with it,
9scaring away the enemy.
10During the Renaissance, the Europeans invented the type of fireworks we know today.
11Modern pyrotechnicians use computers to ignite fireworks from a safe distance.
12And to synchronize their bursts with music.
13Assembling explosives into fireworks is the job of the pyrotechnician.
14Even the tiniest spark of static electricity could set them off.
15So anti-static gloves are a must.
16A firework is made up of separate compartments within a shell.
17The burning fuse explodes one compartment at a time.
18Creating those staggered bursts in the sky.
19The pyrotechnician first glues the main fuse into the bottom of the shell.
20The glue is naturally colorless;
21it is dyed blue so he can tell exactly where he's applying it.
22He puts the bottom aside to work on the second compartment of this two-compartment firework.
23He starts by spooning a powdered explosive into the center.
24Then he caps it;
25here he's working on two fireworks at a time.
26Next step: a brown cardboard shock absorber
27to shield this compartment from the first compartment's explosion.
28Then a corrugated cardboard disc and a plastic spacer.
29It'll take the fuse one and a half seconds to burn through these two components.
30Creating a slight delay between the first explosion and the second.
31Gluing the second compartment together is tricky.
32If it's too tight, it'll stifle the explosion,
33but it has to be tight enough to withstand the delay.
34With the second compartment done, it's time to prepare the first.
35He glues a sleeve onto a case.
36Then fills it with hundreds of stars.
37Stars are what create the flashes of color.
38They're carefully measured explosives mixed with coloring agents.
39Such as magnesium for white, copper salts for blue,
40and charcoal for orange.
41The pyrotechnician must handle them gingerly, or they could detonate.
42Next, he adds comets, another type of exploding decoration.
43He tops it off with gunpowder.
44Finally, he glues the two compartments together.
45Filling the remaining space with the same combination of ingredients.
46Once the shell is full, he glues on the cover.
47And the tighter the better;
48the more pressure that builds up, the bigger and more spectacular the explosion.
49Next, he wraps the fireworks in kraft paper.
50The label uses international color codes to indicate the size of the shell.
51The lift charge, a gunpowder bag with a long fast-action fuse, goes at the base of the shell.
52That's what will send the firework into the sky.
53When they light the main fuse at the top,
54it simultaneously lights two secondary fuses.
55The time-delay fuse inside the shell, running through the compartments of explosives.
56And that long fuse running along the outside down to the lift charge at the base.
57Once the lift charge ignites,
58heat and gas build up inside the launch tube until they explode.
59Propelling the firework close to 1,000 feet skyward.
60Let the light show begin.